The invention relates to a method for controlling the feed of sheets to a sheet-fed printing press having a sheet feeder comprising multiple components, each component being assigned an individual drive and these components being provided for supplying the sheets in a sheet stack, for separating the sheets from a sheet stack and for feeding the sheets to the sheet-fed printing press.
DE 195 05 560 A1 discloses a method for controlling the sheet feed in a sheet processing printing press. In this printing press, the sheets to be printed are taken from the top of a feeder unit stack and conveyed to the installation of the printing press over a predefined conveyor path. At the beginning of the conveyor path, a sheet inspection is performed with regard to double sheets and defective sheets and the sheet conveyance is stopped, depending on the result of the sheet inspection. On detection of a double sheet or defective sheet, withdrawal of additional sheets from the feeder unit stack is stopped immediately and the number of sheets that can still be conveyed into the printing press and printed there before the double sheet or defective sheet in the direction of sheet on the conveyor path reaches the front mark of the installation conveyance is determined. The ink feed is stopped even before the last sheet situated upstream from the double sheet or defective sheet in the direction in conveyance of the sheet enters the printing press. After withdrawal of a sheet from the feeder unit stack has been stopped, sheet conveyance is stopped exactly when the double sheet or defective sheet has reached the installation. Then the number of sheets yet to be fed into the printing press is determined from the distance between the installation and the sheet inspection in combination with the degree of underfeeding in the case of underfed sheet feeding and the format length of the sheets.
One disadvantage of this approach is that in shutdown of the sheet conveyor belt, the underfed sheets may be displaced with respect to one another and cannot approach the printing press again in this state without problems.
EP 1 281 647 B1 therefore presents a method for conveying sheets in a sheet feeder unit of a sheet processing machine by means of which this disadvantage is to be avoided. With this printing press, the rate of travel of the conveyor belt for conveying the fed sheets is variable, independent of the operating speed of the machine in accordance with the predefined speed profiles, so that when starting or stopping of the feeder unit, the conveyor belt can be stopped and/or started in accordance with a predetermined acceleration profile.
DE 102 16 135 A1 discloses a method for controlling the sheet feed to a sheet processing machine having a sheet feeder unit which comprises, among other things, a sheet separator for separating the sheets from a stack and a table with belts or a suction table with belts. The sheets are conveyed to the machine and inspected with regard to double sheets, defective sheets or skewed sheets. If there is such a sheet or if there is a disturbance in the downstream machine, the sheet feed is stopped, in which a sampling device that detects the height level of the stack is provided and the drive of the sheet feeder unit is provided by individual drives, which are controlled by means of an electronic processing unit that is connected to a control unit of the downstream machine. After breaking the connection between the electronic processing unit and the machine control unit, the synchronization of the individual drives is eliminated, so that the individual drives can be operated at will. The individual drives may also be operated optionally in different directions of rotation or brought to a standstill.
This process takes places directly on stoppage of the feeder unit. The disadvantage here is that other driven components of the feeder unit are stopped in an undefined position which makes renewed startup difficult.
Therefore, the object of the present invention is to develop a method by means of which at least two drives of components of the feeder unit are brought to a standstill in a defined position in a targeted manner when the feeder unit is shut down.